Motion vector coding method and motion vector decoding method

1. A decoding system comprising: a recording medium on which multiplexed data is recorded, the multiplexed data being obtained by multiplexing (i) coded picture data that is obtained by coding a moving picture and (ii) audio data that is obtained by coding an audio signal; and a decoding apparatus which decodes the coded picture data and the audio data included in the multiplexed data recorded on said recording medium, wherein the coded picture data is coded using a motion vector coding method for coding a motion vector of each of a plurality of blocks included in the moving picture, the motion vector coding method includes: specifying a neighboring block which is located in a vicinity of a current block to be coded that is included in the moving picture, and which is already coded; judging whether or not the neighboring block has been coded using a motion vector of another block; deriving a predictive motion vector of the current block to be coded using a motion vector of the neighboring block; and coding a motion vector of the current block to be coded using the predictive motion vector, wherein, in the deriving step, if the neighboring block is coded using the motion vector of the another block, a motion vector which is determined by using the motion vector of the another block and is used in coding the neighboring block is used as the motion vector of the neighboring block, and if the neighboring block is not coded using the motion vector of the another block, a motion vector which is detected for the neighboring block and is used in coding the neighboring block is used as the motion vector of the neighboring block, said decoding apparatus includes: a data reading unit configured to read the multiplexed data from said recording medium; a demultiplexing unit configured to demultiplex the multiplexed data read by the data reading unit into the coded picture data and the audio data; a neighboring block specifying unit configured to specify, among the plurality of blocks included in the moving picture that is coded into the coded picture data, a neighboring block which is located in a vicinity of a current block to be decoded and is already decoded; a judging unit configured to judge whether or not the neighboring block has been decoded using a motion vector of another block; a predictive motion vector deriving unit configured to derive a predictive motion vector of the current block to be decoded using a motion vector of the neighboring block; and a motion vector decoding unit configured to decode a motion vector of the current block to be decoded using the predictive motion vector; and a music data decoding unit configured to decode music data, and wherein the predictive motion vector deriving unit is configured to use, as the motion vector of the neighboring block, the motion vector which is determined using the motion vector of the another block and is used in decoding the neighboring block, if the neighboring block is decoded using the motion vector of the another block, and to use, as the motion vector of the neighboring block, a motion vector which is detected for the neighboring block and is used in decoding the neighboring block, if the neighboring block is not decoded using the motion vector of the another block.

2. A decoding apparatus comprising: a receiving unit configured to receive multiplexed data obtained by multiplexing coded picture data that is obtained by coding a moving picture and audio data that is obtained by coding an audio signal; a demultiplexing unit configured to demultiplex the multiplexed data received by said receiving unit into the coded picture data and the audio data; a neighboring block specifying unit configured to specify, among a plurality of blocks included in the moving picture that is coded into the coded picture data, a neighboring block which is located in a vicinity of a current block to be decoded and is already decoded; a judging unit configured to judge whether or not the neighboring block has been decoded using a motion vector of another block; a predictive motion vector deriving unit configured to derive a predictive motion vector of the current block to be decoded using a motion vector of the neighboring block; a motion vector decoding unit configured to decode a motion vector of the current block to be decoded using the predictive motion vector; and a music data decoding unit configured to decode music data, wherein the predictive motion vector deriving unit is configured to use, as the motion vector of the neighboring block, a motion vector which is determined using a motion vector of another block and is used in decoding the neighboring block, if the neighboring block is decoded using the motion vector of the another block, and to use, as the motion vector of the neighboring block, a motion vector which is detected for the neighboring block and is used in decoding the neighboring block, if the neighboring block is not decoded using the motion vector of the another block, the coded picture data included in the multiplexed data is coded using a motion vector coding method for coding a motion vector of each of the plurality of blocks included in the moving picture, the motion vector coding method includes: specifying a neighboring block which is located in a vicinity of a current block to be coded that is included in the moving picture, and which is already coded; judging whether or not the neighboring block has been coded using a motion vector of another block; deriving a predictive motion vector of the current block to be coded using a motion vector of the neighboring block; and coding the motion vector of the current block to be coded using the predictive motion vector, and wherein, in the deriving step, if the neighboring block is coded using the motion vector of the another block, the motion vector which is determined by using the motion vector of the another block and is used in coding the neighboring block is used as the motion vector of the neighboring block, and if the neighboring block is not coded using the motion vector of the another block, the motion vector which is detected for the neighboring block and is used in coding the neighboring block is used as the motion vector of the neighboring block.

3. A decoding method comprising: receiving multiplexed data obtained by multiplexing coded picture data that is obtained by coding a moving picture and audio data that is obtained by coding an audio signal; demultiplexing the multiplexed data into the coded picture data and the audio data; specifying, among a plurality of blocks included in the moving picture that is coded into the coded picture data, a neighboring block which is located in a vicinity of a current block to be decoded and is already decoded; judging whether or not the neighboring block has been decoded using a motion vector of another block; deriving a predictive motion vector of the current block to be decoded using a motion vector of the neighboring block; decoding a motion vector of the current block to be decoded using the predictive motion vector; and decoding music data, wherein, in the deriving step of the decoding method, a motion vector which is determined using a motion vector of another block and is used in decoding the neighboring block is used as the motion vector of the neighboring block, if the neighboring block is decoded using the motion vector of the another block, and a motion vector which is detected for the neighboring block and is used in decoding the neighboring block is used as the motion vector of the neighboring block, if the neighboring block is not decoded using the motion vector of the another block, the coded picture data included in the multiplexed data is coded using a motion vector coding method for coding a motion vector of each of the plurality of blocks included in the moving picture, the motion vector coding method includes: specifying a neighboring block which is located in a vicinity of a current block to be coded that is included in the moving picture, and which is already coded; judging whether or not the neighboring block has been coded using a motion vector of another block; deriving a predictive motion vector of the current block to be coded using a motion vector of the neighboring block; and coding the motion vector of the current block to be coded using the predictive motion vector, and wherein, in the deriving step of the coding method, the motion vector which is determined using the motion vector of the another block and is used in coding the neighboring block is used as the motion vector of the neighboring block, if the neighboring block is coded using the motion vector of the another block, and the motion vector which is detected for the neighboring block and is used in coding the neighboring block is used as the motion vector of the neighboring block, if the neighboring block is not coded using the motion vector of the another block.

4. A semiconductor executing the decoding method of claim 3 .